The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment of any royalty thereon.
The present invention relates generally to radar system waveform generators and more specifically to a design for a waveform generator that multiplexes highly complex combinations of signals using a dual port memory.
In the electronic warfare community there has been a long-standing problem of duplicating radar waveforms. This need has become even more complex with the changes made to modem radar systems. It is not unusual in modem systems to find tracking waveforms, search waveforms, and command data streams all time multiplexed into a frame format. These systems can use amplitude, frequency, or phase shifts on individual pulses. While some systems used in modem anechoic chambers have the ability to replicate these waveforms, many do not. It is also becoming more important for the systems which replicate threat waveforms to be more readily available and portable to suitably check out equipment for test and evaluation. In order to really produce these waveforms accurately, it is necessary for the time resolution of the simulator to match that of the original system. It has been shown that a resolution shift of less than {fraction (1/10)} of one percent can cause some systems to operate improperly.
Samples of waveform generators with dual port memory elements are disclosed in the following U.S. Patents, the disclosures of which are incorporated herein by reference:
U.S. Pat. No. 5,247,303, Sep. 21, 1993, Data quality and ambiguity resolution in a Doppler radar system, Cornelius, Richard H.,
U.S. Pat. No. 5,805,793, Sep. 8, 1998, Stand-alone test device for testing command-response remote terminals, Green Samuel I.,
U.S. Pat. No. 5,795,297, Aug. 18, 1998, Ultrasonic diagnostic imaging system with personal computer architecture, Daigle, Ronald E.,
U.S. Pat. No. 5,389,859, Feb. 14, 1995, Display device including a correction circuit for correcting a position error, and correction circuit for use in such a display device, Stessen, Jeroen H.
U.S. Pat. No. 5,042,000, Aug. 20, 1991, Integral transform method, Baldwin, David R.,
U.S. Pat. No. 5,056,015, Oct. 8, 1991, Architectures for serial or parallel loading of writable control store, Baldwin, David R.
The general purpose of this design was to provide the ability to replicate the waveform of radar systems. Modern day radar signals are getting very complex with signals that multiplex command data to missiles; as well the traditional problem of seeing reflected energy from targets. Due to this highly complex nature, it is important to replicate the signal with very high fidelity. Many modern avionics systems are trying to derive information from this radar signal. To be able to test these systems, it is necessary to be able to generate appropriate signals and observe the response from the equipment under test.
The present invention includes a portable waveform generator system that uses a dual port memory to multiplex complex waveforms for a radar transmitter. In one embodiment a laptop is used to specify the frequency, pulse width, chip configuration, etc. for the waveform generator. The waveform generator outputs up to two-frequency waveform signals that are multiplexed by a combiner in the memory and output to the radar transmitter.
The actual waveform generator includes a clock-based system whose pulse durations and separations were set by counters that use the same fundamental clock frequency of the radar to be simulated. This pulse generator is loaded from a laptop computer. The output pulses are used to control pin switches to switch various frequencies, amplitudes, or phases as required for the particular radar being simulated. The result is a system with very good fidelity that will fit in a suitcase, and is very portable.